Well done. Your symptoms sound familiar with the intermittent, alternating center vent, then defrost vent. In my case, I notice that only when the A/C is engaged. Then, cold air comes out the side and center vents initially, but soon, the center vents are not blowing and the side vents are blowing more air, and sometimes, the defrost is blowing cold, too (but not always). I realize that one or more of the vac pods is bad. Questions: does the recirculator flap operate even when the RECIRC switch isn't on? Is there anything noticeable, like an audible opening/closing sound, or increased/reduced airflow when the RECIRC switch is pressed? What I'm getting at, is how you would know if the recirc system is even working? The 10 minutes it took you, did that include removing glovebox and the two recirc vac pods? Is it likely that installing new pods then would take only a few more minutes? Thanks.

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't